Source: https://www.researchgate.net/profile/Abdelouahab-Zaatri/publication/237435560_Optimisation_du_rendement_d'un_systeme_photovoltaique_par_poursuite_du_soleil/links/02e7e525da36dea787000000/Optimisation-du-rendement-dun-systeme-photovoltaique-par-poursuite-du-soleil.pdf